Python table.b方法代码示例

# 需要导入模块: from sqlalchemy import table [as 别名]
# 或者: from sqlalchemy.table import b [as 别名]
def _joincond_trim_constraints(
            cls, a, b, constraints, consider_as_foreign_keys):
        # more than one constraint matched.  narrow down the list
        # to include just those FKCs that match exactly to
        # "consider_as_foreign_keys".
        if consider_as_foreign_keys:
            for const in list(constraints):
                if set(f.parent for f in const.elements) != set(
                        consider_as_foreign_keys):
                    del constraints[const]

        # if still multiple constraints, but
        # they all refer to the exact same end result, use it.
        if len(constraints) > 1:
            dedupe = set(tuple(crit) for crit in constraints.values())
            if len(dedupe) == 1:
                key = list(constraints)[0]
                constraints = {key: constraints[key]}

        if len(constraints) != 1:
            raise exc.AmbiguousForeignKeysError(
                "Can't determine join between '%s' and '%s'; "
                "tables have more than one foreign key "
                "constraint relationship between them. "
                "Please specify the 'onclause' of this "
                "join explicitly." % (a.description, b.description)) 

# 需要导入模块: from sqlalchemy import table [as 别名]
# 或者: from sqlalchemy.table import b [as 别名]
def with_for_update(self, nowait=False, read=False, of=None):
        """Specify a ``FOR UPDATE`` clause for this :class:`.GenerativeSelect`.

        E.g.::

            stmt = select([table]).with_for_update(nowait=True)

        On a database like Postgresql or Oracle, the above would render a
        statement like::

            SELECT table.a, table.b FROM table FOR UPDATE NOWAIT

        on other backends, the ``nowait`` option is ignored and instead
        would produce::

            SELECT table.a, table.b FROM table FOR UPDATE

        When called with no arguments, the statement will render with
        the suffix ``FOR UPDATE``.   Additional arguments can then be
        provided which allow for common database-specific
        variants.

        :param nowait: boolean; will render ``FOR UPDATE NOWAIT`` on Oracle
         and Postgresql dialects.

        :param read: boolean; will render ``LOCK IN SHARE MODE`` on MySQL,
         ``FOR SHARE`` on Postgresql.  On Postgresql, when combined with
         ``nowait``, will render ``FOR SHARE NOWAIT``.

        :param of: SQL expression or list of SQL expression elements
         (typically :class:`.Column` objects or a compatible expression) which
         will render into a ``FOR UPDATE OF`` clause; supported by PostgreSQL
         and Oracle.  May render as a table or as a column depending on
         backend.

        .. versionadded:: 0.9.0

        """
        self._for_update_arg = ForUpdateArg(nowait=nowait, read=read, of=of) 

# 需要导入模块: from sqlalchemy import table [as 别名]
# 或者: from sqlalchemy.table import b [as 别名]
def select_from(self, fromclause):
        """return a new :func:`.select` construct with the
        given FROM expression
        merged into its list of FROM objects.

        E.g.::

            table1 = table('t1', column('a'))
            table2 = table('t2', column('b'))
            s = select([table1.c.a]).\\
                select_from(
                    table1.join(table2, table1.c.a==table2.c.b)
                )

        The "from" list is a unique set on the identity of each element,
        so adding an already present :class:`.Table` or other selectable
        will have no effect.   Passing a :class:`.Join` that refers
        to an already present :class:`.Table` or other selectable will have
        the effect of concealing the presence of that selectable as
        an individual element in the rendered FROM list, instead
        rendering it into a JOIN clause.

        While the typical purpose of :meth:`.Select.select_from` is to
        replace the default, derived FROM clause with a join, it can
        also be called with individual table elements, multiple times
        if desired, in the case that the FROM clause cannot be fully
        derived from the columns clause::

            select([func.count('*')]).select_from(table1)

        """
        self.append_from(fromclause) 

# 需要导入模块: from sqlalchemy import table [as 别名]
# 或者: from sqlalchemy.table import b [as 别名]
def select_from(self, fromclause):
        r"""return a new :func:`.select` construct with the
        given FROM expression
        merged into its list of FROM objects.

        E.g.::

            table1 = table('t1', column('a'))
            table2 = table('t2', column('b'))
            s = select([table1.c.a]).\
                select_from(
                    table1.join(table2, table1.c.a==table2.c.b)
                )

        The "from" list is a unique set on the identity of each element,
        so adding an already present :class:`.Table` or other selectable
        will have no effect.   Passing a :class:`.Join` that refers
        to an already present :class:`.Table` or other selectable will have
        the effect of concealing the presence of that selectable as
        an individual element in the rendered FROM list, instead
        rendering it into a JOIN clause.

        While the typical purpose of :meth:`.Select.select_from` is to
        replace the default, derived FROM clause with a join, it can
        also be called with individual table elements, multiple times
        if desired, in the case that the FROM clause cannot be fully
        derived from the columns clause::

            select([func.count('*')]).select_from(table1)

        """
        self.append_from(fromclause)